But then, there is a third kind of GUI: couch interfaces. With their media center software, both Microsoft and Apple have been quite innovative in this space. The more I use couch interfaces, the more I want a couch interface for almost every desktop application: For example, if I am on the couch, I don't want to leave it to quickly check my email. Any kind of widget such as weather, dictionary or stocks also makes couch-sense.
Note that couch interfaces are a lot like smartphone interfaces: The screen space is greatly reduced and input facilities are limited. Smartphones partially solved the input problem via multi-touch, couch interfaces could do something similar by building small trackpads into remote controls. Wireless keyboards or wireless air mice might also help. But then the Desktop GUI cursor has to be adjusted to couch constraints (by making it larger?).